The present invention relates in general to an actuation attachment for use in connection with electric controlling and/or signalling devices, particularly in connection with emergency circuit breakers. The attachment is of the type which includes electric means for holding a device in its operative position whereby a slider which is suitably mounted in a housing, is controlled by means of a push button. The locking means are arranged in a transverse slot extending in axial direction in an intermediate part of the slider and are urged by means of a biasing spring into stopping recesses formed at axially spaced locations in the inner wall of the housing.
An actuation attachment of this kind for a push button switch is known from the German publication DE-A No. 32 07 725. In this prior art embodiment, the slider is provided with an opening in the form of a transverse bore in which two locking balls are arranged and pressed apart from the other by a spring in locking recesses formed in the housing. Between the slider and the housing and between the slider and the push button, there are arranged springs which according to operational position of the switch urge the slider together with a push button from a first rest position to a second rest position. Consequently, it is sufficient to exert a slight pressure on the push button in order to release the locking balls from the first locking recess whereupon the slider is displaced in jump by a biased spring and the locking balls engage the locking recesses in the operative position. To reset the switch in its inoperative rest position the push button is drawn back in axial direction against the force of both springs until the locking balls again engage the locking recesses in the first rest position. The prior art attachment is designed such that any rotation of the push button is avoided and the attachment is still guarded against overload in such a manner that the switching process is released only by depressing the push button whereupon the switching proceeds fully automatically and any outside control is impossible.
From the German publication DE-A No. 41 13 034 a locking device for circuit breakers is known which prevents unintentional resetting of the circuit breaker and indicates whether the circuit breaker has released by itself or whether it was actuated by its emergency key. For this purpose it is provided with a specially designed arresting slider which is movable transversely in the direction of movement of a driving plunger. The arresting slider prevents the resetting of the circuit breaker. To reset the circuit breaker it is necessary to move a driving key in its starting position.
It is true that these prior art devices make it possible to temporarily block their operating position that means the position after actuation. A common characteristic of the above described devices and also of other commercially available constructions of actuation attachments of this kind is the feature that the release from the rest position, for example during emergency switching off, is always affected by light tipping or touch on the push button. It has been repeatedly proved in practice that release of such prior art actuation attachment is made in many instances fully unintentionally and frequently without being noticed for example when being brushed against by a clothing piece of a passing person or when someone carelessly leans against a switching panel in which the electric device is mounted and the like.